The IRS has determined that it will follow the holding of a famous case in matters where Internet service providers are approached for contents of e-mail.

In Policy Statement 4-120, the service said it will follow the 2010 holding of United States v. Warshak, and obtain a search warrant in all cases when seeking from an ISP the content of email communications stored by the ISP.

“Accordingly, such information will not be sought from an ISP in any civil administrative proceeding,” according to the IRS, which added that existing guidance not in accord with this policy statement will be updated.

In early April, documents released by the American Civil Liberties Union revealed that the IRS was not always compliant with Warshak. (See "IRS Reads Taxpayer E-Mails without Warrant.")